Role of SHP2 phosphatase in KIT-induced transformation: identification of SHP2 as a druggable target in diseases involving oncogenic KIT

Abstract

Intracellular mechanism(s) that contribute to promiscuous signaling via oncogenic KIT in systemic mastocytosis and acute myelogenous leukemia are poorly understood. We show that SHP2 phosphatase is essential for oncogenic KITinduced growth and survival in vitro and myeloproliferative disease (MPD) in vivo.Genetic disruption of SHP2 or treatment of oncogene-bearing cells with a novel SHP2 inhibitor alone or in combination with the PI3K inhibitor corrects MPD by disrupting a protein complex involving p85␣, SHP2, and Gab2. Importantly, a single tyrosine at position 719 in oncogenic KIT is sufficient to develop MPD by recruiting p85␣, SHP2, and Gab2 complex to oncogenic KIT. Our results demonstrate that SHP2 phosphatase is a druggable target that cooperates with lipid kinases in inducing MPD. (Blood. 2012; 120(13):2669-2678) IntroductionGain-of-function mutations in KIT receptor in humans are associated with gastrointestinal stromal tumors (GIST), systemic mastocytosis (SM), and acute myelogenous leukemia (AML). [1][2][3][4] An activating KIT receptor mutation of aspartic acid to valine at codon 814 in mice (KITD814V) or codon 816 in humans (KITD816V) results in altered substrate recognition and constitutive tyrosine autophosphorylation leading to promiscuous signaling. 5,6 Consequently, cell lines and primary BM cells that express the oncogenic KITD814V demonstrate ligand-independent proliferation in vitro and myeloproliferative disease (MPD) in vivo. [5][6][7][8][9] However, the intracellular signals that contribute to KITD814V-induced MPD are not known. Although activating mutations of KIT involving the juxtamembrane domain found in GIST are highly sensitive to inhibition by imatinib mesylate (ie, Gleevec), KIT mutations within tyrosine kinase domain found in SM and AML, including KITD816V, are relatively resistant to imatinib treatment. [10][11][12] Thus, it is vital to identify novel drug targets for diseases involving KITD816V mutation.Emerging data suggest an essential role for SHP2 in MPD. SHP2 is a protein tyrosine phosphatase that is encoded by PTPN11 gene and has been implicated in diverse signaling pathways induced by a number of stimuli, including growth factors, cytokines, extracellular matrix, and even cellular stress. [13][14][15] Given that activating mutations in SHP2 have been found in leukemias and solid tumors, 16,17 efforts are ongoing to define the potential efficacy of SHP2 phosphatase inhibition in diseases bearing SHP2 hyperactivation, either because of activating SHP2 mutations or those in which SHP2 collaborates with other oncogenes. Using genetic approaches, including primary BM cells derived from SHP2 Ϫ/Ϫ and Gab2 Ϫ/Ϫ mice and a novel SHP2 inhibitor, II-B08, identified from a focused library of indole-based salicylic acid derivatives, 18 we demonstrate that SHP2 is essential for KITD814V-induced MPD. We further demonstrate that SHP2 constitutively binds to p85␣ and Gab2 in KITD814V-bearing cells, which can be disrupted by II-B08 resulting in impaired ligand-independent growth in vitro a...

Shp2 and Pten have antagonistic roles in myeloproliferation but cooperate to promote erythropoiesis in mammals

“…Given the leukemogenic effect of activating PTPN11/Shp2 mutations or Shp2 overexpression in different types of human leukemia (30,33,34), Shp2 has emerged as an attractive therapeutic target for mechanism-based treatment of leukemia (30,35). It was demonstrated recently that a Shp2-inhibitory compound corrected oncogenic Kit-triggered MPN in mouse models (36). However, the multifaceted roles of Shp2 and Pten in hematopoietic cells revealed in this study raise caution for clinical use of specific Shp2 inhibitors for patients with Pten mutation or deficiency.…”

Hematopoietic Colony Formation from Human Growth Factor-Dependent TF1 Cells and Human Cord Blood Myeloid Progenitor Cells Depends on SHP2 Phosphatase Function

“…Due to the highly conserved active site shared by all mammalian phosphatases, identification of specific SHP2 phosphatase inhibitors has been difficult; however, within recent years, pharmacologic inhibitors of SHP2 phosphatase function have been identified [29,[46][47][48], and have demonstrated activity in mutant KIT-, gain-of-function PTPN11-, and FLT3-ITD-induced myeloproliferative neoplasms [27][28][29], all of which bear hyperactivation of SHP2. Based on these promising advancements, we anticipate that inhibition of SHP2 phosphatase activity using small pharmacologic molecules may yield a valuable adjuvant approach to therapies for acute myeloid leukemias and myeloproliferative neoplasms bearing SHP2 hyperactivation.…”

“…However, while several knockout and knockdown studies have demonstrated that Shp2 is particularly important in hematopoietic development and hematopoietic stem cell function [20][21][22][23][24][25][26], none of these has directly examined the role of SHP2 phosphatase function in hematopoiesis. This is particularly of relevance, as pharmacologic inhibitors of SHP2 phosphatase activity are currently in development and have demonstrated activity in oncogene-induced myeloproliferative neoplasms [27][28][29]. Thus, the following studies utilized various SHP2 mutants either lacking the SHP2 phosphatase domain or bearing a loss-of-function point mutation or a gain-of-function point mutation reducing or increasing SHP2 phosphatase function, respectively, to define specifically the role of SHP2 phosphatase function in hematopoiesis.…”

Protein tyrosine phosphatase–σ regulates hematopoietic stem cell–repopulating capacity

“…SHP2 is required for the maintenance of HSCs and progenitor cells (8). Gain-of-function mutations in SHP2 cause a myeloproliferative disorder, and SHP2 is essential for oncogenic c-KIT transformation to myeloproliferative disease (9,10). Recently, the intracytoplasmic phosphatase of regenerating liver PRL2 was found to be important for SCFmediated HSC self renewal (11).…”